Abstract: A power supply provides a regulated power factor load to a primary power source, and thus low input current distortion, by monitoring: (A) The input voltage; (B) The power source current, not at the input to the power supply, but rather at a point downstream of an EMI filter and a shunt capacitance in the power supply; and (C) The output DC voltage. The power supply uses these inputs to control the power switching transistors to regulate the phase and amplitude of the monitored current. The phase of the monitored current is controlled primarily by the phase of the input voltage. A differentiating circuit in the feedback loop of the power supply control circuitry causes the monitored current to lag the input voltage by an amount equal to the lead induced in the phase of the input current by the EMI filter and shunt capacitor so that the actual input current to the power supply is in phase with the input voltage.

Abstract: An inverter circuit for a power train has a rectifier for rectifying a three phase AC input and a filter comprising an inductor and capacitor to produce a filtered DC signal for application to the inverter. A high to low voltage transducer receives the filtered DC signal to produce a low voltage output representation thereof. A leading phase shifter shifts the low voltage signal in phase. A sample and hold amplifier receives shifted signal, and a pulse generator generates timing pulses applied to the sample and volt amplifier, whereby the sample and hold amplifier produces an output signal amplitude corresponding to the amplitude of the shifted signal during periods indicated by the pulse generator output. A triangle wave generator provides a triangle wave output to a pulse width modulator, which also receives the output from the sample and hold amplifier to produce an output pulse indicative of the signal level of the filtered DC output.